The present invention relates to a video format converting apparatus, and more particularly, to a video format converting apparatus capable of reducing the number of the line memories which are used when a charge coupled device (CCD) image is converted into a common intermediate format (CIF) image set between respective terminals thereof, to thereby reduce the size of an integrated circuit (IC) of line memories.
In general, a video communications system sends and receives video and voice signals between two locations apart from each other via respective terminals which can send and receive video and audio signals, and allows users located remotely from each other to communication with each other while viewing each other as the case that they are all in the same place. In the video communications system, a CIF is utilized to enable terminals to communicate with each other without considering a video signal system relating to the number of frames to be transmitted per second or the number of scanning lines of a screen. Therefore, each of terminals employing a different video signal system converts a video signal to be transmitted into a CIF to perform an encoding operation, and inversely converts the encoded video signal into a signal which is adapted to a video signal system of the terminal during decoding. In this manner, it is possible to perform video communications between mutually different types of terminals.
A CCD camera is usually used as a pickup device for a video communications system. A vertical resolution of a CCD image picked up in the CCD camera is 240 lines. On the other hand, a vertical resolution of a CIF image which is used in a video communications field is 288 lines. Thus, in order to perform video communications, the CCD image should be converted into the CIF image. That is, a video signal of 240 lines should be converted into a video signal of 288 lines. As a result, a video format converting apparatus for converting a video signal having a vertical resolution of 240 lines into that of 288 lines requires a number of line memories, which causes an IC integrated with the line memories to be larger in size.
To solve the above problems, it is an object of the present invention to provide a video format converting apparatus which can allow implementation of a video communications system capable of reducing the number of line memories which are used for converting a video format of an image, to thereby reduce the size of an IC of line memories.
To accomplish the above object of the present invention, there is provided a video format converting apparatus for use in a video communications system, the video format converting apparatus comprising:
a first line memory for delaying input line image data by a predetermined interval of time and outputting delayed line image data; a first coefficient generator for generating a first weighted coefficient corresponding to the delayed line image data output from the first line memory; a second coefficient generator for generating a second weighted coefficient corresponding to the input line image data; line interpolation means for generating interpolated line image data from the input line image data and the delayed line image data, using the first and second weighted coefficients; a second line memory for delaying the interpolated line image data by the predetermined interval of time; a multiplexer for selecting one of the outputs of the first and second line memories and outputting the selected one; and a controller for controlling the operations of the first and second coefficient generators and the multiplexer so that line image data of a second video format having a second number of lines is output with respect to the input line image data of the first video format having a first number of lines.